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Detnoation Problems
What exactly causes detonation? If detonation is sufficent to cause rod bearings to fail with just minimal run time on motor, will there alsways be signs left on the pistons?
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Re: Detnoation Problems
don't know how to explain exactly the cause (bad gas, bad timing), but I had melted sparkplugs, or also the ceramic part of the spark plug coming out of it's base, leaving the piston to throw the compression out of the engine with a funny noise with it, also had melted valves, with holes in the valves (compression = 0) and broken/melted pistons. the top rings were also kind of spotted. things that make you go, umhhh...
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Re: Detnoation Problems
Dean, I don't know who you are but the next time i'm up there I have to shake your hand. You've got worse luck with boats than I do, just ask Hoghead!
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Re: Detnoation Problems
Originally Posted by kennyo
Dean, I don't know who you are but the next time i'm up there I have to shake your hand. You've got worse luck with boats than I do, just ask Hoghead!
This is how bad it is... My wife is encouraging me to get a harley so I will quit obsesing over this boat...... :( Think about it........ :mad: So anyway, I am getting ready to order one..... :D One of the boat shop owners this weekend told me "Man, you know WAY to much about this stuff to be a CPA"..... I told him the education was not cheap.... |
Re: Detnoation Problems
Originally Posted by jeff32
don't know how to explain exactly the cause (bad gas, bad timing), but I had melted sparkplugs, or also the ceramic part of the spark plug coming out of it's base, leaving the piston to throw the compression out of the engine with a funny noise with it, also had melted valves, with holes in the valves (compression = 0) and broken/melted pistons. the top rings were also kind of spotted. things that make you go, umhhh...
I sent a motor back to the place I got it from, it lasted about an hour, rod bearings on #5 and 6 destroyed. Pistons show no sign of detonation, but the shop says it has to be detonation, otherwise the bearings would not come apart. They have not gotten the motor back yet, but I can see where this is headed, and I need enough ammo to re-direct if the conversation needs it. So far the place I got the motors has been straight, but they have not had to send a new motor yet either......... :rolleyes: |
Re: Detnoation Problems
Some quotes:
Detonation (also called "spark knock") is an erratic form of combustion that can cause head gasket failure as well as other engine damage. Detonation occurs when excessive heat and pressure in the combustion chamber cause the air/fuel mixture to autoignite. This produces multiple flame fronts within the combustion chamber instead of a single flame kernel. When these multiple flames collide, they do so with explosive force that produces a sudden rise in cylinder pressure accompanied by a sharp metallic pinging or knocking noise. The hammer-like shock waves created by detonation subject the head gasket, piston, rings, spark plug and rod bearings to severe overloading. Detonation can be caused by: Lean fuel mixture Fuel octane too low Improper ignition timing Lugging Carbon deposits Excessive milling of heads or block, which will increase compression ratio. Pre-ignition, as the term suggests, is the ignition of the fuel-air mixture before the regular ignition spark from the spark plug. If the regular spark occurs shortly after the pre-ignition, the colliding of the two flame fronts will cause a pinging noise. Preignition causes loss of engine power and can cause severe damage to pistons, rings and valves. Detonation and pre-ignition are so closely related that it is en difficult to distinguish one from the other by sound. Each can lead to the other and either condition can cause extensive engine damage. |
Re: Detnoation Problems
Forgot to add:
Pre-ignition can be caused by: Carbon deposits that remain incandescent Spark plugs too hot a heat range Spark plugs not firmly seated against gasket Detonation or the condition leading to it Sharp edges in combustion chamber Valves operating at higher than normal temperature because of excessive guide clearance or improper seal with valve seats. Overheating Ignition crossfiring. Induced voltage in spark plug wires that run parallel to each other for long distances |
Re: Detnoation Problems
Detonation severe enough to quickly damage rod bearings would also do serious damage to pistons and valves. It also is not likely isolated to two cylinders (unless fuel injected). Since 5 and 6 share a journal on the crank the failure of even 1 half of a bearing set can blitz all 4 halves on 2 rods.
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Re: Detnoation Problems
Could it be the crank on that jurnal be bad?[big] to tight? etc. I would think if it detinated enough to get the rod bearing that it would show up in the spark plug first. Also the rod could be on the small side ,ck it with a AG gage.
I know on my nitrous motors it takes out the plug first :( |
Re: Detnoation Problems
That is what I thought, so thanks for confirming that, now I do not feel like I am loosing it or something........
plugs, pistons, and head gasket all look good......... I kept thinking something of the magnatude to destroy rod bearings by compressing them would most assuradely show up somewhere else too.... I hope the conversation with the motor guy goes well tomorrow.... |
Re: Detnoation Problems
Bearings not clearanced correctly? Who line honed the block? Oil flow problems? Did you loose oil pressure? Were the rod bolts new? Sounds more like an assembly issue. Those are what I would be looking at if your pistons are intact. Detonation will most certainly be seen on the piston and spark plug for that matter. Usually the spark plug fails too.
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Re: Detnoation Problems
this was a new, GM crate motor, we could not pull rod and main caps because of warranty issues, which is why I do not know what the bearings looked like, other than the peices that were EVERYWHERE....
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Re: Detnoation Problems
Originally Posted by dean51267
this was a new, GM crate motor, we could not pull rod and main caps because of warranty issues, which is why I do not know what the bearings looked like, other than the peices that were EVERYWHERE....
Factory motors can have issues too, I still can't see how detonation would take out a main or rod bearing. You just got a motor built on a Monday morning or Friday afternoon....... :( Maybe your oil pump pick up fell off? What did the inside of your filter look like? If you had a bearing going bad there should be some pieces in the filter before the motor let go. |
Re: Detnoation Problems
They usally will brass out in the rod and not the cap
http://www.fierojoe.com/plugins/gara...od_bearing.jpg http://www.fierojoe.com/plugins/gara...od_bearing.jpg |
Re: Detnoation Problems
this has some fair picks
http://images.google.com/imgres?imgu...005-33,GGLD:en Detonation explained http://zhome.com/ZCMnL/PICS/detonation/detonation.html some info I found What evidence does detonation leave? What should the piston look like? Absence of normal carbon deposits Hole melted at side of piston dome and progressing behind top ring land Broken spark plug ceramic at tip of plug or very white ceramic Holes burnt into top of combustion chamber Impact damage to piston dome http://www.sacskyranch.com/deton.htm http://www.hastingsmfg.com/Service%2...detonation.htm What is detonation / knock? Under normal conditions, the combusting air and fuel mixture inside the combustion chamber ignites in a controlled manner. The mixture is ignited by the spark, normally in the center of the cylinder, and a flame front moves from the spark towards the outside of the cylinder in a contolled burn. Detonation occurs when air and fuel that is ahead of the flame front ignites before the flame front arrives because it becomes overheated. Under these conditions, the combustion becomes uncontrolled and sporadic and often produces a pinging noise, or a "knock" noise when the conditions become worse. So far, detonation sounds cool... why is it bad? Detonation is definitely not cool. Detonation causes sudden pressure changes in the cylinder, and extreme temperature spikes that can be very damaging on engine pistons, rings, rods, gaskets, bearings, and even the cylinder heads. Even the best engine components cannot withstand severe detonation for more than a few seconds at a time. More severe detonation obviously leads to more severe forms of engine damage. If there is enough heat and pressure in the combustion chamber, detonation can begin to occur before the spark plug even fires, which would normally initiate the combustion. Under these circumstances, known as "pre-ignition", the piston may be travelling up towards a wave of compressed, exploding gas. These are the worst kinds of detonation conditions, and can bend con-rods and destroy pistons. What causes detonation? Detonation occurs when several conditions / factors inside the combustion chamber exist at the same time. Increased compression, high temperatures, lean fuel/air mixture, advanced ignition timing, and lower octane fuels are all factors that PROMOTE detonation conditions. The good news is that, because there are so many factors in play, you can always find a way to eliminate detonation if it exists. |
Re: Detnoation Problems
spark plug detonation pick
http://images.google.com/imgres?imgu...LD:en%26sa%3DN here are some picks of bearring failures http://www.bobistheoilguy.com/bearin...aranalysis.htm |
Re: Detnoation Problems
3 Attachment(s)
My Nitrous screw up,lean.
When I tore down the motor it didnt show any signs of detination in the top of the rod bearing.It showed a little crank flexing on the outer edges of the mains,but this was a 425hp shot on a 358ci engine.It also didnt push out the head gasket either :drink: It only showed 50% leak down on that hole |
Re: Detnoation Problems
3 Attachment(s)
pics of teardown
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Re: Detnoation Problems
3 Attachment(s)
more
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Re: Detnoation Problems
3 Attachment(s)
more 2
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Re: Detnoation Problems
That looks like more than bearing material that came apart :eek:
There a swirling carbon tracking on top of one piston. Look at this http://www.sacskyranch.com/deton.htm |
Re: Detnoation Problems
Originally Posted by Strip Poker 388
That looks like more than bearing material that came apart :eek:
also the cooling passages were not well cleaned before assembly, I am not sure if this matters in this situation..... motro never got hot, timming was checked several times, a merc tech was with me when it went, and it only made noise for MAYBE 15 seconds before we got it shut down. The oil was not burnt (it only had about an hour on it). Since I have had problems the tech and I both were hyper sensitive to possible problems..... |
Re: Detnoation Problems
Originally Posted by dean51267
I know, I know, but I do not knwo WHAT it is, it almost looked like a metal "goo"........ but there was also bearing metal in the pan and oil galley and # 5 and 6 rods were lose.........
also the cooling passages were not well cleaned before assembly, I am not sure if this matters in this situation..... motro never got hot, timming was checked several times, a merc tech was with me when it went, and it only made noise for MAYBE 15 seconds before we got it shut down. The oil was not burnt (it only had about an hour on it). Since I have had problems the tech and I both were hyper sensitive to possible problems..... What oil galley?? Did you look at any other rods and main bearings?? It will be hard to tell now if there was a prob with clearance etc with those 2 now :( Rob |
Re: Detnoation Problems
Rereading your post I got ahead of myself.... What GM crate motor is it? The CR? a rebuilt engine?
Also the cylinder walls looks dark in one pick |
Re: Detnoation Problems
Dean have you established whether these blocks have the correct bypass valve insatlled for marine use?
If they dont have the correct 30psi valve or have them plugged, most of your oil will bypass the filter and cooler through the block |
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